Complex grease containing inorganic salt thickener



United States PatentO COMPLEX GREASE CONTAINING INORGANIC SALT THICKENER Arnold-J. Morway, Clark-Railway, and John J. Kolfenbach, North Plainfield, N. J., assignors to Esso Research and Engineering Crnpany, a corporation of Delaware No Drawing. Application October 6, 1954 Serial No. 460,762

Claims. (Cl. 252-21) Thisinvention relates 'to lubricatinggrease composi tions and more particularly relates to high temperature lubricating grease compositions which contain a complex thickener. .Still more particularly the lubricating grease compositions of-this invention contain a'thickener which is a complex of a soap, a salt of a low molecularweight ,carboxylic acid and an inorganic salt, the molar ratio of salt to soap being a high multiple. The invention also relates to a method of preparing such lubricating grease compositions.

Soap-salt complexes are well known in the art for thickening lubricating oils to produce lubricating grease compositions. These complex thickeners havebeen employed for high temperature greases and consist of combinations of metal salts of low molecular weight carboxylic acids with metal soaps of high molecular weight fatty acids. Normally the soaps and salts have been employed in proportions in the range of ab0ut'0.5 to 3 moles of salt per mole of soap. Because 'the' thickening eitect of the salt is rather low, it has been generally considered desirable tomaintainthe mole ratio of salt to soap below 3 since above'a mole ratio of about 3 the total requirement of soap-salt thickener needed to make greases of satisfactory penetration characteristics was found to be quite high.

However, recently it has been found that by drastically increasing the salt content and with it the metal content :of soap-salt complexes, entirely new properties may be built into these complexes which greatly increase their value as grease thickeners. More specifically, it has been found that complexes of metal salts of low molecular weight carboxylic acids with metal soaps of high molecular weight carboxylic acids which contain at least 7'moles and up to as much as 40 moles or more,

preferably about 8 to 25 moles, of the low molecular weight acid per mole of the high molecular weight acid have-outstanding load-carrying, dispersant, and various other beneficial characteristics in addition to thickening properties comparable to: soap-salt complexes containing substantially lower proportions of :low. molecular weight carboxylic acids. These particular thickeners and their utilization in lubricating grease compositions are .described in detail in the co-pending Molway and Kolfenbach application Serial No. 387,527, filed October 21, 1953, of which this application is a continuation-in-part.

It has now been found that properties of these high salt content greases, such as structural stability, lubrication life at elevated temperatures, and water resistance, may be improved by employing a complex containing, in addition to the aforementioned soaps and salts, an inorganic salt. The lubricating oils employed in making the greases of the present invention include synthetic oils as well as mineral oils. The soaps utilized in the complex thickeners of the present invention are preferably alkaline earth metal soaps of high molecular weight carboxylic acids having about 12 to 30 carbon atoms, preferably those having about 16 to 22 ,carbon atoms per molecule. The low molecular weight carboxylic acids employed to form salts in the complex thickener are those containing about 1 to 6 carbon atoms per molecule, acetic acid being especially preferred. As to the *inorganic salts employed in the thickener, these salts m'ay be, for 'example, fin'e'ly divided or colloidal materials such as silicates or they may be salts which are capable of formin'ga complex with the low molecular weight carboxylic acid. 'The greases of this invention are prfe'pare'tl by forming a mixture of the high 1 molecular weight :carboxylic acid, the low molecular weight carboxylic acid, the inorganicsaltand a' basic'reacting compound of preferably an alkaline earth metal in the lubricating-oil in grease-making proportions and heating the. mixture to:a temperature inth"e ra n'ge of about '450 to 600 11F. to dehydrate :the mixture and to "promote formation of the resulting complex "thickener. The molar ratio of low molecular weight carboxylic acid radicals .tohigh molecular weight carboxylic acid radicals in the resultant complex .isat least about 7:1 and preferably in the range of about=8,:1 to 25 :1. .In general, the grease compositions of this invention will contain about-5 to 35% by weight and preferably about 15 tof3'0% by weight .of the complex thickener which contains .in "the range of (about 1'0 to 50% by weight and preferably about 25 'to'40% by weight of the inorganic salt.

A wide variety of inorganic salts may be employed in forming the complex thickeners of the lubricating greases of 'the present invention. The' salt-sare preferably alkaline earth metal salts suchas those of calcium, barium, and -magnesium. One .class of inorganic salts which may; be used to advantage rarewithose whichnare finely dividedgor'colloidalinform f andIhaveyan'average particle size ,diameter preferably of about 0.1 'micron or less. Included inethis.classaresilicatesof magnesium, calcium, strontium, barium, .etc., synthetic zeolites, mixed silicate gels. and mixedfsilicate hydroxide gels as well as complex mixtures of these various types. These particular inorganic salts are well known to those skilled 'in the art' since th'ey'have beenhe'retofore used as thickeners in simple lubricatinggreases. The preferred inorganic salts df thi's class -are the 'alkalineearth metal silicates, particularly those-of calcium and 'magnesium.

..1 i notheratype-:of inorganic salts which may be employedito iform theacomplex thickener of the present invention are those inorganic salts which form complexes withvthe low molecular weight'carboxylic "acids.

These. particular complexes of .the inorganic .salt a and the low molecular weight acid are akin to the hydrated inorganic salts, that is, inorganic salts containing water of crystallization. For example, a particularly preferred inorganic salt is calcium nitrate which forms an acid-salt :complex having the general formula eCa g [0 1 1402] sodium phosphate such as Na P O Na HPO and NaH PO potassium phosphate, sodiumborate, potassium borate, and the like. I

The high molecular weight carboxylic acids useful for the purposes of .the present invention ar ejthe grease forming carboxylic acids. Suitable carboxylic acids include those having about 12 to 30 carbon atoms and preferably those having about 16 to 22 carbon atoms per molecule. These acids may be derived from saturated or unsaturated naturally occurring or synthetic fatty materials. The fatty acids normally used in the manufacture of conventional greases, particularly the more saturated acids, are preferred. Examples of such acids include stearic, hydroxy stearic, such as 12-hydroxy stearic, di-hydroxy stearic, polyhydroxy stearic and other saturated hydroxy fatty acids, arachidic, hydrogenated fish oil and tallow acids, etc. However, unsaturated acids, such as oleic, ricinoleic and similar acids may likewise be used. It will be understood, of course, that the naturally occurring or synthetic fatty materials mentioned above may be directly employed in the grease-making process to form soaps of high molecular weight earboxylic acids by treatment thereof with the basic metal reacting compound in the grease-making process.

Suitable low molecular weight acids include saturated and unsaturated aliphatic mono-carboxylic acids having about 1 to 6 carbon atoms such as formic, acetic, propionic, furoic, acrylic, and similar acids including their hydroxy derivatives such as lactic acid, etc. Formic and particularly acetic acids are preferred.

The metal component of the complex thickeners of this'invention is preferably an alkaline earth metal such as calcium, barium, or magnesium, the preferred alkaline earth metal being calcium. Mixtures of alkaline earth metals may be employed, if desired.

The lubricating oil employed to produce lubricating grease compositions in the method of this invention may be conventional grease-making mineral oils as well as synthetic lubricating oils. The synthetic oils include synthetic lubricating oils having a viscosity of at least 30 SSU at 100 F. such as esters of monobasic acids (e. g. ester of C Oxo alcohol with C Oxo acid, ester of C Oxo alcohol with octanoic acid, etc.), esters of dibasic acids (e. g. di-Z-ethyl hexyl sebacate, dinonyl adipate, etc.), esters of glycols (e. g. C x0 acid diester of tetraethylene glycol, etc.), complex esters (e. g. the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of Z-ethyl-hexanoic acid, complex ester formed by reacting one mole of tetraethylene glycol with two moles of sebacic acid and two moles of 2- ethyl hexanol, complex ester formed by reacting to gether one mole of azelaic acid, one mole of tetraethylene glycol, one mole of C Oxo alcohol, and one mole of C Oxo acid), esters of phosphoric acid (e. g. the ester formed by contacting three moles of the mono methyl ether of ethylene glycol with one mole of phosphorus oxychloride, etc.), halocarbon oils (e. g. the polymer of chlorotrifluoroethylene containing twelve recurring units of chlorotrifluoroethylene), alkyl silicates (e. g. methyl polysiloxanes, ethyl polysiloxanes, methylphenyl polysiloxanes, ethyl-phenyl polysiloxanes, etc.), sulfite esters (e. g. ester formed by reacting one mole of sulfur oxychloride with two moles of the methyl ether of ethylene glycol, etc.), carbonates (e. g. the carbonate formed by reacting C 0x0 alcohol with ethyl carbonate to form a half ester and reacting this half ester with tetraethylene glycol), mercaptals (e. g. the mercaptal formed by reacting 2-ethyl hexyl mercaptan with formaldehyde), formals (e. g. the formal formed by reacting C Oxo alcohol with formaldehyde), polyglycol type synthetic oils (e. g. the compounds formed by condensing butyl alcohol with fourteen units of propylene oxide, etc.), or mixtures of any of the above in any proportions. Quite generally the mineral or synthetic oils should have a viscosity within the range of about 35 to 200 SSU at 4 210 F. the flash points of about 350 to 600 F. Lubricating oils having a viscosity index of 100 or higher may be employed. However, oils of lower viscosity index such as below 60 V. I. give better yields.

The complex thickener of this invention which contains the soap, the salt of the low molecular weight carboxylic acid and the inorganic salt generally will represent about 5 to and preferably about 15 to 30% of the total lubricating grease composition. In the complex thickener, the molar ratio of low molecular weight carboxylic acid radical to high molecular weight carboxylic acid radical should be at least about 7:1 and preferably is in the range of about 8:1 to 25:1. The proportion of the inorganic salt in the complex thickener should be in the range of about 10 to 50% by weight and preferably in the range of 25 to by weight based on the total complex thickener. In general, the lubricating oil will represent about 55 to 95% by weight of the total lubricating grease composition.

The grease-making procedure employed to prepare the lubricating grease compositions of this invention includes the formation of a mixture of the high molecular weight carboxylic acid, the low molecular weight carboxylic acid, the inorganic salt and a basic reacting compound of preferably an alkaline earth metal in a portion or all of the lubricating oil in grease-making proportions followed by heating the mixture to a temperature in the range of about 450 to 600 F. to dehydrate the mixture and to promote formation of the resulting complex. Thereafter the grease is cooled and the remainder of the lubricating oil may then be added in those cases where only a portion was initially utilized.

the saponifiable synthetic oil thereto after the resultant composition has been cooled. However, if the lubricating oil which is to be utilized is entirely a saponifiable synthetic lubricating oil, or if it is desired for some reason or another to add a portion of the saponifiable synthetic lubricating oil to the mineral oil and/ or the nonsaponifiable synthetic oil prior to the formation of the complex thickener, it is advisable to initially dehydrate the composition at a relatively low temperature such as in the range of about 220 to 300 F. prior to heating the composition to a temperature above about 450 F. to thereby promote a formation of the complex.

It will be understood that if so desired in the grease: making procedure mixtures of high molecular weight carboxylic acids, mixtures of low molecular weight carboxylic acids or mixtures of inorganic salts may be em ployed to form lubricating greases in accordance with this invention. It will be further understood that conventional grease additives, as, for example, anti-oxidants such as phenyl alpha naphthylamine, corrosion inhibitors such as sorbitan monooleate, tackiness agents such as polybutene or high molecular weight polymerized acrylic esters, load-carrying compounds such as sulfurized and/or phosphorus and/or chlorine containing oil-soluble materials, and the like may be added prior, during or after the heating step as will be apparent to those skilled in the art.

The invention will be more fully understood by reference to the following examples. It is pointed out. however, that the examples are given for the purpose of illustration only and are not to be construed as limiting the scope of the present invention in any way.

EXAMPLE 1 The following lubricating grease composition was prepared in accordance with this invention:

Hydrogenated 'fish oi l acids corresponding to commercial stearic acidin average number of carbon'atoms and in degree of saturation.

A naphthenic type mineraloil having a yiscos1tyof 55 -SSU at 210 F.

Calcium' nitrate, "Ca (NO ej) -4H O, was heated to 350 and held at this temperature while stirring until substantiallyallfof the water of crystallization had been removed. flhe hot molten product' wasthen poured into glacial acetic-acid in which it dissolvedito forma rather "viscous fluid. The proportions were selected such that 1 mole of Ga (N03 was addefd to -"3 moles, of 'CH COOH The hydrofol acids S'lftheilimeand 'theflubr icating oil were then charged to 'afire=heated grease'kettle and the temperaturewasjraised to"-l'3-5- F. "The wasi ls ada d a d h ati'n tinlte b u 1 0" whic e u' 1 9 abou 21 h fli r wa then coo1ed1oj2 0 whe efthej'p eny lp a h h lam ne a dd s id ..u. th o9' o F. an h mbssaizi d.

ee ie:

" mooth'homored grked. na'ia' s 242,-

. err .000 t okes-.- rma as" 1%).(252 t .77'.-F-+.60 s ke h The above data show-that the product has no melting Poiflt nd sf u tab e for use inwct bnd t s- T pwdna a so h qadi idation e ist nc and is s i a o i s. e i in ant -itic iqnb ann s operating a 'e at d empera u e a normal or h g peed.

EXAMP E 2 The a l ina ii rl a s ase w po itio wasp ra sd n saqtd ncs wi h thisn n g e Hydrogenated fish oil acids corresponding to commercial stearic acid innumber of carbon atoms per molecule and in degree of saturation.

-"A synthetic magnesium silicatehaving the following properties:

Absorption, water percent by weight 100-200 Dfinsity, loose weight lbs. /cu. ft 55328 Particle size average. microns Surface area sq. meters/gramnu 175-290 Refractive index 1.521:o4

A naphthenic type mineral oil having a viscosity of 55 SSU at 210 F Preparation The hydrofol acids 51, .the hydrated ilime, the synthetic magnesium silicate .and the lubricating oil were charged to ,a fire-heatedgreasekettle and warmed while mixing .to 135 .F. The acetic acid was then charged and heating continued to about 500 F., which required about 2 hours. At this temperature, heating was discontinued and the grease cooled while working to 250 F.

. a which point th .p e lp aph hy ni a ed ;and the grease further cooled ito 200 F. The grease was then .Gaulin homogenized,v filtered and packaged.

Properties Appearance Excellent, smooth uniform product.

. Percent free alkalinity as 'NaOH 0.24.

Penetrations, 77 F. min/'10:

Unworked 171. Worked, 60 strokes 195. Worked, 100,000 str0kes 276. Dropping ipoint, F; None. Water resistance (210 F.) Excellent. Norma Hoifmann oxidatiom'hours,

to :give 5.p. s. *i. drop 225. Wheel bearing Itest (6 hours at 220 'F.) Passno leakage or indication of corrosion.

These data indicate. that the above grease is suitable for services operating at ambient to high temperatures. It may be employed under wet conditions due to water insolubility. The penetration data indicate that the grease is structurally stable to long mechanical working and under these conditions doesnot thin out excessively or fluidize.

EXAMPLE 3 The lubricating grease of Example 2 was diluted with additional mineral oil of the type employed to prepare the lubricatinggrease of Example 2 to produce the following composition:

Formulation Percent Grease of Example, .2 70 Lubricating oil '30 Preparation The grease of Example 2 and the mineral oil were mix'ed'together at room temperature in a Hobart mixer andwere then Gaulin homogenized.

form'product. Penetration, 77 F., mm./10:

Unworked 245.

-Worked, 60 strokes 275.

Worked, 100,000 strokes 290.

Wheel hearing test Excellent, no

leakage.

By dilution of the grease of the previous example, a softer product is formed which is more suitable to dispensing from mechanical or hand-operated lubrication equipment. This softer product retains all of the excellent characteristics of its harder base.

EXAMPLE 4 The following lubricating grease composition was prepared in accordance with this invention:

' Formulation Ingredients: 1 Percent weight Hydrofol acids 51 4.00 Acetic acid (glacial) 4.00 Hydrated lime 3.30 Calcium silicate 2 5.30 Phenyl alpha naphthylamine Lubricating oil Hydro enated fish oil acids corresponding to commercial stearic ac d in number 01. carbon atoms per molecule and in degree of saturation.

: A synthetic calcium silicate having the following proper res:

Absorption, water, 1percent. by weight 275-400 Density, loose weig t, lbs/cu. ft 12-15 8.0-9.5 Particle size, average, microns 0.03-0.05 Surface area, sq. meters/gram 175-200 Refractive ind x 1.52-1.54

A naphthenic type mineral oil havln a viscosi of 50 SSU at 210 F. g ty Preparation The Hydrofol acids 51, the hydrated limefthe calcium silicate and the lubricating oil were'charged toa fire-heated grease kettle and warmed while mixing to 135 F. The acetic acid was then charged and heating continued to 500 R, which required about 2 hours. At this temperature, heating was discontinued and the grease cooled while working to 250 F., at whichpoint the phenyl alpha naphthylamine was added and the grease further cooled to 200 F. The grease was then Gaulin homogenized, filtered and packaged.

Properties What is claimed is:

1. A lubricating grease composition comprising a major proportion of a lubricating oil and about 5 to35% by weight, based on the total composition, of a complex of an alkaline earth metal soap'of a high molecular weight monocarboxylic acid having from about 12 to 30 carbon atoms per molecule, an alkaline earth metal salt of a low molecular weightmonocarboxylic acidhaving about 8 1 to 6 carbon atoms per molecule, and an inorganic salt selected from the group consisting of alkaline earth metal nitrates and alkaline earth metal silicates, the molar ratio of low molecular weight carboxylic acid radicals to high molecularweight carboxylic acid radicals-in said complex being about 7:1 to 25:1 and the proportion of said inorganic salt intsaid complex being in the range of about 10 to 50% by weight, said complex being prepared at a temperature of about 450 to 600 F.

2. A method for preparing an improved high temperature lubricating grease which comprises forming in greasemaking proportions, a mixture of a high molecular weight monocarboxylic acid having from about 12 to 30 carbon atoms per molecule, a low molecular weight monocarboxylic acid having about 1 to 6 carbon atoms per molecule, an inorganic salt selected from the group consisting of alkaline earth metal nitrates and silicates and a basic reacting compound of an alkaline earth metal, in a lubricating oil, heating the mixture to a temperature in the range of about 450 to 600 F. to dehydrate the mixture and to promote formation of the resulting complex of: a soap, a salt of the low molecular, weight carboxylic acid and the inorganic salt, the molar ratio of low molecular weight carboxylic acid radicals to high molecular weight carboxylic acid radicals in said complex being about 7:1 to 25:1, and said inorganic salt constituting about 10 to 50 weight percentof said complex.

3. A lubricating grease composition comprising a major proportion of a mineral lubricating oil and in the range of about 15 to 30% by weight, based on the total composition, of a complex of a calcium soap of a high molecular weight carboxylic acidhaving in the range of about 12 to 30 carbon atoms per molecule, calcium acetate and calcium nitrate, the; molar ratio of acetic acid radical to high molecular Weight carboxylic acid radical being in the range of about 8:1 to 25 :1 and the proportion of said calcium nitrate in said complex being in the range of about 25 to 40% by weight, said complex being prepared at a temperature of about 450 to 600 F.

4. Composition according to claim 3 wherein said high molecular weight carboxylic acid comprises hydrogenated fish oil acids. i i

5. 'A lubricating grease composition comprising a major proportion of a mineral lubricating oil and in the range of about 15 to 30% by weight, based on, the total composition, of a complex of a calcium soap of a high molecular weight carboxylic acid having from about 12 to 30 carbon atoms per molecule, calcium acetate and an alkaline earth metal silicate, the molar ratio of acetic acid radical'to high molecular weight carboxylic acid radical being in the range of about 8:1 to 25:1 and the proportion of said alkaline earth metal silicate in said complex being in the range of about 25 to 40% by weight, said complex being prepared at a temperature of about 450 to 600 F.

6. Composition according t to claim 5 wherein said high molecular weight carboxylic acid comprises hydrogenated fish oil acids. i

7. Composition according to claim 5 wherein said silicate is finely divided magnesium silicate having an averageparticle 'si'ze of=less than about 0.1- micron.

8. Composition according to claim 5 wherein said silicate is finely divided calcium silicate having an average particle size of less than about 0.1 micron.

9. A method for preparing an improved lubricating grease which comprises forming in grease-making proportions, a mixture of hydrogenated fish oil acids averaging about 18 carbon atomsper molecule, Ca(NO -3C H O, and hydrated lime in a mineral lubricating oil and heating the mixture to a temperature in the range of about 450 to 600 F. to dehydrate themixture and to promote formation oi the resulting complexof the soap of the hydrogenated fish oil acids, calcium acetate and calcium nitrate, the molar ratio of low molecular weight carboxylic acid radicals to high molecular weight carboxylic acid radicals in said complex being in the range of 8:1 to 25:1, and said inorganic salt constituting about 10 to 50 weight percent of said complex.

10. A method for preparing an. improved lubricating grease which comprises forming in grease-making proportions, a mixture of hydrogenated fish oil acids averaging about 18 carbon atoms per molecule, glacial acetic acid, hydrated lime and a finely divided alkaline earth metal silicate in a mineral lubricating oil and heating the mixture to a temperature in the range of about 450 to 600 F. to dehydrate the mixture and to promote formation of the resulting complex of the soap of the hydrogenated fish oil acids, calcium acetate and said alkaline earth metal silicate, the molar ratio of low molecular weight carboxylic acid radicals to high molecular weight carboxylic acid radicals in said complex being in the range of 8:1 to 25:1, and said inorganic salt constituting about 10 to 50 weight percent of said complex.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,082 Zimmer et al. Jan. 25, 1949 10 2,417,428 McLennan Mar. 18, 1947 2,417,429 McLennan Mar. 18, 1947 2,417,430 McLennan Mar. 18, 1947 2,417,432 McLennan Mar. 18, 1947 2,417,433 McLennan Mar. 18, 1947 2,455,659 Duncan Dec. 7, 1948 2,455,892 Fraser Dec. 7, 1948 2,468,098 Morway et a1 Aug. 14, 1949 2,483,800 Zimmer et a1. Oct. 4, 1949 2,487,080 Swenson Nov. 8, 1949 2,513,680 Shott et al. July 4, 1950 2,575,286 Morway et al. Nov. 13, 1951 2,583,605 Sirianni et al. Jan. 29, 1952 2,583,607 Sirianni et a1 Jan. 29, 1952 2,607,735 Sproule et al. Aug. 19, 1952 2,656,315 Eckert Oct. 20, 1953 2,698,299 Giammaria Dec. 28, 1954 OTHER REFERENCES Boner: Lubricating Greases, copyright 1954, Reinhold Pub. Co., New York, N. Y., pages 645, 721 and 771-775 

1. A LUBRICATING GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF A LUBRICATING OIL AND ABOUT 5 TO 35% BY WEIGHT, BASED ON THE TOTAL COMPOSITION, OF A COMPLEX OF AN ALKALINE EARTH METAL SOAP OF A HIGH MOLECULAR WEIGHT MONOCARBOXYLIC ACID HAVING FROM ABOUT 12 TO 30 CARBON ATOMS PER MOLECULE, AN ALKALINE EARTH METAL SALT OF A LOW MOLECULAR WEIGHT MONOCARBOXYLIC ACID HAVING ABOUT 1 TO 6 CARBON ATOMS PER MOLECULE, AND AN INORGANIC SALT SELECTED FROM THE GROUP CONSISTING OF ALKALINE EARTH METAL NITRATES AND ALKALINE EARTH METAL SILICATES, THE MOLAR RATIO OF LOW MOLECULAR WEIGHT CARBOXYLIC ACID RADICALS TO HIGH MOLECULAR WEIGHT CARBOXYLIC ACID RADICALS IN SAID COMPLEX BEING ABOUT 7:1 TO 25:1 AND THE PROPORTION OF SAID INORGANIC SALT IN SAID COMPLEX BEING IN THE RANGE OF ABOUT 10 TO 50% BY WEIGHT, SAID COMPLEX BEING PREPARED AT A TEMPERATURE OF ABOUT 450 TO 600*F. 